In order to find and produce hydrocarbons e.g. petroleum oil or gas, a well may be drilled in rock (or other) formations in the Earth.
After the well bore has been drilled in the earth formation, tubulars will be introduced into the well. The tubular covering the producing or injecting part of the earth formation is called the liner. Tubulars used to ensure pressure and fluid integrity of the total well are called casing. Tubulars which bring the fluid to surface from the earth formation are called tubing. The outside diameter of the liner is smaller than the inside diameter of the well bore covering the producing or injecting section of the well, providing thereby an annular space, or annulus, between the liner and the well bore, which consists of the earth formation. Sometimes this annular space can be filled with cement or sealed off with packers preventing axial flow along the liner. However if fluids need to enter or leave the well, small holes will be made penetrating the wall of the liner and the cement in the annulus therewith allowing fluid and pressure communication between the earth formation and the well. The holes are called perforations. This design is known in the oil and natural gas industry as a cased hole completion.
An alternative way to allow fluid access from and to the earth formation can be made, a so called open hole completion. This design is used when the earth formation is deemed not to collapse with time, and then the well does not have a liner covering the earth formation where fluids are produced from or injected in to. The well designs discussed here can be applied to vertical, horizontal and/or deviated well trajectories.
To produce hydrocarbons from an oil or natural gas well, a method of maintaining reservoir pressure and sweeping hydrocarbons is via water injection or water-flooding. In water-flooding, wells may be drilled in a pattern which alternates between injector and producer wells. Water is injected into the injector wells, whereby oil in the production zone is swept or displaced into the adjacent producer wells.
Knowledge of the water injection and oil/gas production can be determined by conveying a suite of petrophysical tools in the well to gather data. This can be done in a cased hole or an open hole completion.
Conveying petrophysical tools into wells, especially horizontal wells is limited to the depth that can be reached with means of conveyance suitable for particular well dimensions, typical conveyance via coiled tubing, workstring or wireline tractor. These conveyance methods can be prevented in reaching the total depth of the well by restrictions, tortuosity, tool limits or drag, the latter two particularly seen in open hole completion.
In order to reach the total depth of these wells to fully understand production and injection, it may be advantageous to have an apparatus and system and method to convey to total depth to gather data.